1. Field of the Invention
The present invention relates to a picking unit for a fluid jet loom and, more particularly, to a method and device for controlling the checking pin of a drum type weft measuring and storing device for a fluid jet loom.
2. Description of Related Art
When the yarn package on a fluid jet loom is changed during a picking operation, the size of the balloon and the resistance to unwinding the yarn from the yarn package changes due to a sudden change in the diameter of the yarn package and in the physical properties of the yarn. Consequently, the picking speed varies even though the operating conditions of the fluid jet loom are unchanged. The variation of the picking speed causes the time at which the extremity of a picked weft arrives at a predetermined position on the arrival side opposite to the picking side of the fluid jet loom to vary, so that the fluid jet loom is unable to operate normally.
Accordingly, the picking speed must be changed, or else the synchronous operation of the fluid jet loom will be disrupted, to ensure a correct picking operation synchronous with the principal motions of the fluid jet loom.
Means for changing the picking speed are disclosed, for example, in Japanese Laid-Open Patent Publication No. 58-18446 and Japanese Laid-Open Utility Model Publication No. 60-136379. According to those known means, when a yarn package is changed, the pressure of the picking fluid is changed or the timing of the operation of the picking nozzle is changed. However, since the device controlled by those known methods is the picking nozzle, the methods are not directly applicable to controlling the checking pin of a drum type weft yarn storing device.
Japanese Laid-Open Utility Model Publication No. 61-82973 discloses a further method for controlling the picking operation, in which the checking pin releasing timing is changed according to the amount of the picking force. However, since this method does not include any means for dealing with a package change, the same is not suitable for solving the problem associated with variations in the picking operation attributable the package change.